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Biomedical subjects

A Grüters

Publications and source records attributed to A Grüters.

At least 19 recordsLinked to original sources
PubMed1999

Ocular manifestations in children and adolescents with thyrotoxicosis.

Thyrotoxicosis is a rare disorder in childhood and adolescence. The frequency ranges from 0.1 in 100000 in young children to 3.0 in 100000 in adolescents and the most frequent cause is Graves' disease. Few children and adolescents suffer from thyrotoxicosis during the course of autoimmune thyroiditis and non-autoimmune hyperthyroidism due to constitutively active mutations of the TSH-receptor have been reported in single patients with neonatal hyperthyroidism and rare familial cases. From a survey of the literature it is apparent that infiltrative ophthalmopathy is very rare in children and adolescents. Milder ocular manifestations as retraction of the upper eyelid, upper lid lag and "staring eyes" are reported in varying frequencies ranging from 25 to 60% of all patients. In our own series of 43 children and adolescents (34 females, 9 males) with thyrotoxicosis only 16 (37%) had clear ocular manifestations of upper lid retraction, lid lag and slight protrusio bulbi. However, only three of of them had soft tissue involvement and significant exophtalmus. In none of the patient corneal or optic nerve involvement or paralysis of the extraorbital muscles was observed. Newborns with congenital hyperthyroidism due to maternal Graves' disease seem to present significant transitory ocular manifestations more frequently, but again no infiltrative ophtalmopathy requiring specific therapy is present. Recently at least four different newborns with congenital thyrotoxicosis due to gain-of-function mutations of the TSH-receptor have been reported, who also had significant ocular manifestations. The presence of staring eyes, slight proptosis and lid retraction in these newborns without any autoimmune or inflammatory process supports the hypothesis that these ocular manifestations are caused by the increased thyroid hormone actions. The involvement of the eyes is usually transitory in newborns as well as in children and adolescents and the symptoms usually disappear when euthyroidism is restored. The administration of steroids therefore is restricted to the rare severe cases with eye muscle or soft tissue involvement. There are no reports on surgical decompression or orbital irradiation therapy of ophtalmopathy in children and adolescents, which again indicates that ocular involvement in thyrotoxicosis in children and adolescents is less frequent and much less severe than in adults.

Adolescent↗
PubMed1999

Alterations of neonatal thyroid function.

Recent progress has been made in understanding the pathogenesis of neonatal thyroid disorders. Autosomal recessive inheritance of mutations of the thyroid peroxidase and thyroglobulin genes has been described in some patients with congenital hypothyroidism (CH) and a family history of CH. Autosomal recessive inheritance of mutations of the thyrotrophin (TSH) receptor gene has also been reported in patients with CH and thyroid hypoplasia, and autosomal dominant mutations of the PAX8 gene have been described in patients with different forms of thyroid dysgenesis. These discoveries are important for patients with CH diagnosed by neonatal screening, as these patients will have normal fertility. The molecular genetic analysis of mutations of the TSH gene in patients with familial and sporadic cases of isolated central CH, who are missed by TSH screening programmes, now enables rapid diagnosis and appropriate therapy in the neonate. In newborn infants with severe non-autoimmune hyperthyroidism, autosomal dominant gain-of-function mutations in the TSH receptor gene have been demonstrated. In these patients, molecular genetic studies are extremely helpful in therapeutic decision making, as early thyroid ablation is the only effective treatment that avoids the sequelae of long-term hyperthyroidism. Molecular genetic studies are therefore useful in the diagnostic work-up of neonatal thyroid alterations.

Congenital Hypothyroidism↗
PubMed1999

Bilateral Wilms tumor in a boy with severe hypospadias and cryptochidism due to a heterozygous mutation in the WT1 gene.

Mutations in the WT1 gene causing Wilms tumors were first reported in WAGR syndrome (Wilms tumor, Aniridia, Genitourinary malformation, mental Retardation) and Denys Drash syndrome (pseudohermaphroditism, Wilms tumor, nephropathy), but only in a few patients with hypospadias and cryptorchidism without other signs of Denys Drash (DDS) or WAGR syndrome WT1 mutations were identified. We report a boy, who was born in 1989 with hypospadias and bilateral cryptorchidism. Previous karyotyping and endocrine studies had ruled out any known cause of male pseudohermaphroditism. Subsequently, he developed a bilateral Wilms tumor, which was detected by palpation at the age of 15 months during a routine visit by the general pediatrician. Because of its extensive size, surgery and chemotherapy were needed for treatment. Analysis of the WT1 gene was performed 5 y after diagnosis and revealed a C to T transition in one allele generating a stop codon at codon 362 and subsequently leading to a truncated protein with loss of its ability to bind to DNA. No signs of DDS or WAGR syndrome are present in the boy. The work up of this patient and the so far known few comparable cases from the literature lead to the conclusion that in newborns with severe urogenital malformations not due to known chromosomal or endocrine disorders mutational screening of the WT1 gene should be performed, to evaluate the high risk of developing a Wilms tumor. We favor mutational screening in these patients as an easy tool for investigation, because in the future it will probably decrease the necessity of frequent control visits in patients without a WT1 mutation.

Base Sequence↗
PubMed1999

Severe congenital hypothyroidism due to a homozygous mutation of the betaTSH gene.

Isolated TSH deficiency leading to hypothyroidism seems to be a rare condition, escaping the diagnosis by neonatal screening programs, which are based on the primary determination of TSH. This is the first report of a case with an autosomal recessive TSH defect caused by a homozygous mutation of the betaTSH gene that was diagnosed in the early neonatal period. Hypothyroidism in the first child of apparently unrelated parents was suspected because of the classical symptoms of congenital hypothyroidism, which were fully expressed already on the 11th day of life. Routine neonatal TSH-screening on the 4th day of life had been normal, but subsequent determination of serum thyroid hormone levels revealed almost undetectable levels and thyroid hormone substitution was immediately started. Because there was no indication for other pituitary hormone deficiencies, sequence analysis of the betaTSH gene was initiated. A homozygous T deletion in codon 105 was found resulting in a change of a highly conserved cysteine to valine followed by eight altered amino acids and a premature stop codon due to the frame-shift. This altered betaTSH is a biologically inactive peptide. Because of the early development of severe symptoms, it is possible that this altered TSH suppresses the physiologic constitutive activity of the unliganded TSH receptor. Rapid molecular diagnosis in this patient clarified the diagnosis without additional endocrine and imaging studies and it is concluded, that symptoms of hypothyroidism in the neonatal period should result always in an immediate comprehensive work-up of thyroid function including molecular genetic studies irrespective of the screening result.

Congenital Hypothyroidism↗
PubMed1998

V2 vasopressin receptor dysfunction in nephrogenic diabetes insipidus caused by different molecular mechanisms.

Loss-of-function mutations in the V2 vasopressin receptor (AVPR2) gene have been identified as a molecular basis for X-linked nephrogenic diabetes insipidus (NDI). Herein, we describe a novel deletion mutation at nucleotide position 102 (delG102) found in a Russian family resulting in a frameshift and a truncated receptor protein. Furthermore, we analyzed the AVPR2 gene of two other unrelated boys with NDI from our patient clientele. These patients showed previously described mutations (R137H, R181C). In-depth characterization of the three mutant AVPR2s by a combination of functional and immunological techniques permitted further insight into molecular mechanisms leading to receptor dysfunction. Premature truncation of the AVPR2 (delG102) led to a drastically reduced receptor protein expression in transfected COS-7 cells and, as expected, precluded specific AVPR2 functions. As indicated by different ELISA and binding studies, the R137H mutant was almost completely retained in the cell interior. In contrast to previous studies, the few mutant receptors in the plasma membrane displayed a low (2.3-fold above basal) but significant ability to stimulate the Gs/adenylyl cyclase system. In contrast to the latter mutation, the R181C mutant is properly delivered to the cell surface but the mutation interferes with high affinity vasopressin binding. Impaired ligand binding is reflected in an about 100-fold shift of the concentration-response curve toward higher vasopressin concentrations with only slightly reduced agonist potency.

Amino Acid Sequence↗
PubMed1998

Severe early-onset obesity, adrenal insufficiency and red hair pigmentation caused by POMC mutations in humans.

Sequential cleavage of the precursor protein pre-pro-opiomelanocortin (POMC) generates the melanocortin peptides adrenocorticotrophin (ACTH), melanocyte-stimulating hormones (MSH) alpha, beta and gamma as well as the opioid-receptor ligand beta-endorphin. While a few cases of isolated ACTH deficiency have been reported (OMIM 201400), an inherited POMC defect has not been described so far. Recent studies in animal models elucidated a central role of alpha-MSH in the regulation of food intake by activation of the brain melanocortin-4-receptor (MC4-R; refs 3-5) and the linkage of human obesity to chromosome 2 in close proximity to the POMC locus, led to the proposal of an association of POMC with human obesity. The dual role of alpha-MSH in regulating food intake and influencing hair pigmentation predicts that the phenotype associated with a defect in POMC function would include obesity, alteration in pigmentation and ACTH deficiency. The observation of these symptoms in two probands prompted us to search for mutations within their POMC genes. Patient 1 was found to be a compound heterozygote for two mutations in exon 3 (G7013T, C7133delta) which interfere with appropriate synthesis of ACTH and alpha-MSH. Patient 2 was homozygous for a mutation in exon 2 (C3804A) which abolishes POMC translation. These findings represent the first examples of a genetic defect within the POMC gene and define a new monogenic endocrine disorder resulting in early-onset obesity, adrenal insufficiency and red hair pigmentation.

Adrenal Insufficiency↗
PubMed1998

PAX8 mutations associated with congenital hypothyroidism caused by thyroid dysgenesis.

Permanent congenital hypothyroidism (CH) is a common disease that occurs in 1 of 3,000-4,000 newborns. Except in rare cases due to hypothalamic or pituitary defects, CH is characterized by elevated levels of thyroid-stimulating hormone (TSH) resulting from reduced thyroid function. When thyroid hormone therapy is not initiated within the first two months of life, CH can cause severe neurological, mental and motor damage. In 80-85% of cases, CH is associated with and presumably is a consequence of thyroid dysgenesis (TD). In these cases, the thyroid gland can be absent (agenesis, 35-40%), ectopically located (30-45%) and/or severely reduced in size (hypoplasia, 5%). Familial cases of TD are rare, even though ectopic or absent thyroid has been occasionally observed in siblings. The pathogenesis of TD is still largely unknown. Although a genetic component has been suggested, mutations in the gene encoding the receptor for the thyroid-stimulating hormone (TSHR) have been identified in only two cases of TD with hypoplasia. We report mutations in the coding region of PAX8 in two sporadic patients and one familial case of TD. All three point mutations are located in the paired domain of PAX8 and result in severe reduction of the DNA-binding activity of this transcription factor. These genetic alterations implicate PAX8 in the pathogenesis of TD and in normal thyroid development.

Amino Acid Sequence↗
PubMed1998

A conserved tyrosine residue (Y601) in transmembrane domain 5 of the human thyrotropin receptor serves as a molecular switch to determine G-protein coupling.

In the human thyroid, the wild-type thyrotropin receptor (TSHR) couples to adenylyl cyclase and phospholipase C and constitutively increases intracellular cAMP levels. The first human TSHR sequence submitted differs from subsequently cloned wild-type receptors by an exchange of a conserved Y residue within transmembrane domain 5 (TM5) for an H residue. We did not detect the Y601H mutant in 263 European individuals, but confirmed the homozygous occurrence of TSHR-Y601. Expression of TSHR-Y601H in COS-7 cells revealed a loss of constitutive cAMP production and selective lack of TSH-induced phosphoinositide hydrolysis, whereas agonist-induced cAMP formation remained unaltered. Analysis of several mutant receptors (Y601A, Y601D, Y601F, Y601K, Y601P, Y601S, Y601W, Y601Delta) did not show restoration of constitutive activity and dual signaling, thus suggesting a functional role of a properly spaced hydroxyl group at position 601. Molecular modeling revealed that the formation of a hydrogen bond between the hydroxyl group of Y601 in TM5 and the carbonyl oxygen of A623 in the peptide backbone of TM6 is critical for the receptor to adopt active conformations that impart wild-type signaling properties. Our findings indicate that multiple active receptor states underlie coupling of a G-protein-coupled receptor to different G-proteins.

Animals↗
PubMed1998

Severe congenital hyperthyroidism caused by a germ-line neo mutation in the extracellular portion of the thyrotropin receptor.

Gain of function mutations in the TSH receptor (TSHR) have been identified as the molecular basis for congenital and acquired forms of autonomous thyroid function. Herein, we report the molecular characterization of a case of severe congenital hyperthyroidism with a history of hyperthyroidism in the paternal aunt and the paternal grandmother, who were both found to be heterozygous for a mutation (R528H) located in exon 10 of the TSHR gene. Functional expression of the mutant TSHR-R528H in COS-7 cells, however, did not result in constitutive activity of the TSHR. Subsequent analysis of exons 1-9 led to the detection of an additional heterozygous mutation (S281N) in the patient, but not in other family members. Interestingly, the latter mutation is located in the extracellular domain of the TSHR, and functional studies revealed a marked increase in basal cAMP levels when the mutant receptor was expressed in COS-7 cells. To address the question of whether both mutations were present on the same allele, a double mutant TSHR (S281N/R528H) was generated and characterized. These functional studies in conjunction with RT-PCR analysis of thyroid tissue obtained from subtotal thyroidectomy performed at the age of 6 yr revealed that the patient bears two distinct mutations on different alleles: the familial paternal R528H mutation to be regarded as a polymorphism and a de novo mutation (S281N) on the maternal allele accounting for the clinical picture. Thus, the main conclusions to be drawn from this case are 1) a search for mutations in cases of congenital nonautoimmune hyperthyroidism should not remain restricted to exon 10 of the TSHR gene, because germ-line gain of function mutations of the TSH receptor can be located outside of the transmembrane core of the receptor; and 2) this case illustrates the necessity for careful functional characterization of any novel mutation before a causal relationship to hyperthyroidism can be established.

Alleles↗
PubMed1997

[Neonatal Basedow's disease in twins from a mother with severe T3 hyperthyroidism].

HISTORY AND CLINICAL FINDINGS: Dizygotic twin sisters were born to a woman who, shortly before becoming pregnant, had developed Graves' disease with markedly elevated triiodothyronine (T3) levels and highly positive TSH receptor antibody titres (TRAb: 169 mU/ml). From the second week of life onwards they had a goitre and hyperexcitability, tachycardia and failure to thrive were noted. In addition, twin I had mild exophthalmos. As thyrostatic treatment of the mother was very difficult, intrauterine hypothyroidism or transitory hyperthyroidism had presumably occurred in the twins. INVESTIGATIONS: Twin I had maximal thyroxine (T4) concentration of 26.2 micrograms/dl, while it was 24.7 micrograms/dl in twin II with suppressed TSH. Both twins had high concentrations of TRAb and antibodies against thyroid peroxidase. DIAGNOSIS, TREATMENT AND COURSE: With the diagnosis of neonatal Graves' disease established, both twins were treated with propranolol (2 mg/kg.d) and phenobarbitone (2-4 mg/kg.d). Twin I, whose symptoms were more severe, also received propylthiouracil (5 mg/kg.d) until euthyroidism had been achieved. Although twin II became euthyroid spontaneously, she gained weight only slowly and microcephaly developed together with definite motor and mental retardation. It remains unclear whether these were consequences of intrauterine hypothyroidism or post-partum hyperthyroidism. CONCLUSION: Graves' disease during pregnancy demands interdisciplinary collaboration between gynaecologist, physician and paediatrician to prevent severe sequelae in the children. Early risk assessment is possible by measuring the TSH receptor antibody titre in umbilical blood.

Adrenergic beta-Antagonists↗
PubMed1997

Congenital hyperthyroidism.

Congenital hyperthyroidism is a very rare disease. But, for each affected child it has to be considered as a serious condition because of the negative impact of hyperthyroidism on fetal and postnatal development. If the manifestation occurs during fetal life tachycardia, cardiac arrhythmia, growth retardation and, most significant, prematurity are the consequences. Postnatal signs of hyperthyroidism are irritability, tachycardia, hypertension, poor weight gain and thyroid enlargement. Even cardiac failure may occur if hyperthyroidism is severe and treatment not adequate which explains the high early mortality rate of 16%. The main complication of persistent hyperthyroidism in the neonatal period and during infancy is craniosynostosis. Severe developmental delay or even mental retardation can be the consequence of inadequate high T4-levels during fetal and neonatal life. Congenital hyperthyroidism was first recognized in infants born to mothers with Graves' disease. The description of transplacental passage of the maternal thyroid stimulating antibodies elucidated the molecular mechanism in this major group of patients with "autoimmune congenital hyperthyroidism". In contrast to this transient, self-limited character of "autoimmune congenital hyperthyroidism", due to the clearance of maternal antibodies from the infant's circulation, some cases of persistent congenital hyperthyroidism without signs of thyroid autoimmunity have been recognized. Activating mutations in the thyroid-stimulating hormone receptor were described recently as the underlying molecular pathogenesis in this group of "non-immune congenital hyperthyroidism". Therefore the possibility of a molecular differential diagnosis of both groups of congenital hyperthyroidism now exists and opens the opportunity of optimal treatment for each patient.

Autoimmune Diseases↗
PubMed1997

Results of the screening program for congenital hypothyroidism in Berlin (1978-1995).

Screening for congenital hypothyroidism for all newborns of the former western parts of the city of Berlin was instituted in 1978 by determination of the TSH levels in dried filter paper blood spots of the 3rd to 5th day of life. Since 1991 the newborns of the former eastern parts have been also included in the same screening program. From 1978 to 1995 a total number of 104 newborns with permanent congenital hypothyroidism have been detected resulting in a prevalence of congenital hypothyroidism of 1:3800. The etiological diagnosis of hypothyroidism was made by imaging studies (ultrasonography or 99mTc scintigraphy) and assessment of serum thyroglobulin and thyroid hormone levels. Using this approach in 37 children (30 female, 7 male) the diagnosis of athyrosis, in 20 children (15 female, 5 male) the diagnosis of ectopy and in 21 children (18 female, 3 male) the diagnosis of thyroid hypoplasia was made, 16 children (8 female, 8 male) had a normally sized gland and 4 (1 female, 3 male) had congenital goiter. In 86% of all patients the age at onset of thyroxine (L-T4) replacement therapy was 8 or 9 days of life (3-42 days) and the median initial L-T4 dose was 14 micrograms/kg/day (10-16 micrograms/kg/day). The intellectual outcome of 77 children (2-16 years) was studied and normal scores for the intelligence (IQ) and developmental (DQ) quotients were found in 71 (92%). Outcome was not correlated to the age at onset of treatment, the initial dose and the severity of hypothyroidism, but there was a positive correlation of the socioeconomic status of the family and the IQ of the patients. The results of the screening program in Berlin document that an early and efficient thyroxine replacement can normalize the intellectual outcome of patients with congenital hypothyroidism independent of the severity of the disease as assessed by the residual thyroid function detectable at diagnosis.

Berlin↗
PubMed1997

Small thyroid volumes and normal iodine excretion in Berlin schoolchildren indicate full normalization of iodine supply.

Iodine deficiency is the major cause of an increase in thyroid gland volume in infants and children. In this field study we monitored the iodine supply and its effect on the thyroid gland volume in prepubertal and pubertal children in the eastern and western parts of the city of Berlin, so far considered as an area with borderline iodine deficiency. The thyroid gland volume was determined by ultrasound in 1080 (f = 552, m = 528) children aged 3-15 years, and was correlated to age, body-surface area and iodine excretion, which was measured in a first-morning spot urine. The mean iodine concentration was 115.8 micrograms iodine/g creatinine (12.2 micrograms iodine/dl urine), with no significant differences between eastern parts with 114.5 micrograms iodine/g creatinine (12.3 micrograms iodine/dl urine) vs 116.7 micrograms iodine/g creatinine (12.0 micrograms iodine/dl urine) in the western parts of the city. This good iodine supply of the children was surprising compared to former studies in children and adults. Moreover this normalization of the iodine excretion was reflected by smaller thyroid gland volumes in the children. The volume was found to increase with age and was 2.4 +/- 1.1 ml in prepubertal (Prader and Largo: f < or = 10.9 ys, m < or = 11.5 ys) children, compared to 4.3 +/- 1.7 ml in pubertal children. The goiter prevalence, calculated on this data was below 5%. Among all children there were only 11 (aged 8-13 ys) with abnormal findings of the thyroid gland on ultrasound: 6 with small nodules, 1 girl with a thyroid-cyst, 2 girls had an inhomogenous echo structure and 2 girls presented with a hemithyroidea. This study shows that the iodine supply of the children in Berlin has improved, resulting in smaller sized thyroid glands, compared to those which have been previously published for Germany (Müller-Leisse 1988; Klingmüller, 1991; Menken, 1992), but they correspond well to volumes described in countries with sufficient iodine supply.

Adolescent↗
PubMed1997

Neonatal TSH screening--an instrument of iodine supplementation monitoring in Bulgaria in comparison to Berlin--a preliminary report.

The challenge to eradicate iodine deficiency disorders (IDD) by the year 2000 worldwide will have positive consequences for more than 20 million people suffering from IDD. This is the main and common goal for the developing but also for a lot the developed countries. Sensitive tools like neonatal thyroid screening (NTS) can be used in order to make changes in iodine supplementation more transparent and to have a dynamic target oriented approach. The comparison between six districts in Bulgaria and Berlin revealed despite of some positive changes after the fortification of the iodine supplementation program still existing iodine deficiency in Bulgaria which is more profound than in Berlin in 1990. The shift to higher TSH-values in the Black-Sea region, classified by goitre-prevalence in 1956 as non-endemic for iodine deficiency, needs further investigation. Besides of iodine deficiency an influence of iodine-containing disinfectants and/or goitrogens is possible.

Berlin↗
PubMed1997

Hypoparathyroidism and deafness associated with pleioplasmic large scale rearrangements of the mitochondrial DNA: a clinical and molecular genetic study of four children with Kearns-Sayre syndrome.

In four children with hypoparathyroidism and deafness as initial major manifestations of Kearns-Sayre syndrome, a unique pattern of mitochondrial DNA rearrangements was observed. Hypocalcemic tetany caused by PTH deficiency started between age of 6-13 y and was well controlled by small amounts of 1.25-(OH)2-cholecalciferol. Rearranged mitochondrial genomes were present in blood cells of all patients and consisted of partially duplicated and deleted molecules, created by the loss of 7813, 8348, 8587, and 9485 bp, respectively. The deletions were localized between the origins of replication of heavy and light strands and encompassed at least eight polypeptide-encoding genes and six tRNA genes. Sequence analysis revealed imperfect direct repeats present in all rearrangements flanking the break-points. The duplicated population accounted for 25-53% of the mitochondrial genome and was predominant to the deleted DNA (5-30%) in all cases. The proportions of the mutant populations (30-75%) correlated with the age at onset of the disease. We conclude that, unlike heteroplasmic deletions, pleioplasmic rearrangements may escape selection in rapid-dividing cells, distribute widely over many tissues, and thus cause multisystem involvement. Hypoparathyroidism and deafness might be the result of altered signaling pathway caused by selective ATP deficiency.

Child↗